1. Field of the Invention
Apparatuses and methods consistent with the present general inventive concept relate to a printing control device, an image forming apparatus, and an image forming method. More particularly, the present general inventive concept relates to a printing control device, an image forming apparatus, and an image forming method, which can convert a bitmap image to a sketch image in print data and print the print data in which the bitmap image is converted to the sketch image.
2. Description of the Related Art
In modern printing devices, saving of a consumption agent, in particular, a toner, is very important and has significant ecological impact. In this regard, there are a lot of patents and publications devoted to draft printing or toner saving in printing devices via special processing to a rendered (rasterized) image of a printed page.
A general method for printing in a draft mode is decreasing an optical density for the whole image during rasterization. For electrophotographic and ink-jet printers, the decrease of the optical density is realized by means of an increase of brightness to pixels of rasterized graphical objects before rasterization thereof, which uses a halftoning or a change in halftoning threshold. For example, U.S. Pat. No. 5,646,670 proposes an apparatus and a method to reduce toner consumption by a decrease of overall image density for color image. U.S. Pat. No. 5,946,450 describes a method to reduce toner or ink consumption in rasterized image by a change of channel transfer function, which reduces the image in size as a whole. U.S. Pat. No. 6,476,836 describes an image forming apparatus where image pixels having values larger than a threshold are converted into a predetermined pattern received as a result of PWM (pulse width modulation), while for pixels of image having values not larger than the threshold, no output is made.
However, the decrease of optical density for the whole page seriously deteriorates the printed hardcopy in quality. If the optical density for the whole page is decreased, edges of characters in a text become ragged, the text becomes inaccurate in shape and poor in readability, and the text is sometimes not recognizable by OCR applications, as compared with a normal mode. In order to provide significant toner saving, the whole printed page has to be notably impaired, for example, 50% or more, in quality
At present time, a majority of printed documents contains pictures, which are stored and transferred as color or grayscale bitmaps. For instance, web-pages, as a rule, contain a lot of bitmaps. Printing these bitmaps leads to a significant consumption of toner. To address this problem, there are several technical solutions, providing a capability to skip a printing of such bitmaps. For instance, US laid-open patent application No. 2009/0195811 describes a method for printing only text objects from PDF.
U.S. Pat. Nos. 5,751,433 and 5,751,434 describe systems and methods for draft printing by changing a function of channel transform in dependence from the type of printed object. It causes only the bitmaps to worsen in quality, and allows the text to preserve a quality thereof for draft printing.
U.S. Pat. No. 6,972,857 describes a method for controlling a use of consumable on a printing device. For every page, a page cost is set, and its value depends on the number of dots to be printed. If the page cost exceeds a preset threshold, at least one of known toner saving techniques is applied.
It is necessary to note that the existing approaches for draft printing either worsen the quality of the whole printed page or totally skip the printing of bitmaps, which leads to important information loss. On the other hand, sometimes, if the quality of draft printing is quite high, the amount of saved toner is insignificant.
Also, the majority of proposed methods for draft printing does not provide accurate estimation of saved toner.